A semiconductor device has many layers on a silicon substrate, and these layers are formed on the silicon substrate by a deposition process. Such a deposition process has several important issues, and these issues are essential to evaluation of deposited films and selection of deposition methods.
The first issue is the quality of deposited films. The quality means a composition, a contamination level, a defect density, and mechanical and electrical properties of the deposited films. The compositions of the films are varied according to deposition conditions, and are important to obtain a specific composition.
The second issue is the uniform thickness of the deposited films throughout a wafer. Particularly, the thickness of a film deposited on the upper surface of a nonplanar pattern having steps is important. Whether or not the thickness of the deposited film is uniform is determined through a step coverage, which is defined by a value obtained by dividing the minimum thickness of the film deposited on a stepped portion by the thickness of the film deposited on the upper surface of the pattern.
Another issue relating to deposition is space filling. This filling includes gap filling, in which gaps between metal lines are filled with an insulating film including an oxide film. The gaps are provided to physically and electrically insulate the metal lines from each other.